Home HeatingWhat’s That Sound? Understanding Why a Boiler is Noisy

June 20, 2019by oil4wales

Is your boiler making weird sounds? Here are a few reasons why you have a noisy boiler and what you can do to fix your boiler!

The average five-bedroom home in the UK costs £137 for gas and electricity per month.

When something is wrong with your electrical or heating systems, those energy costs can skyrocket quickly. And if you have a noisy boiler and an increasing energy bill, chances are that something is wrong.

A noisy boiler can be the sign of a number of different problems. To diagnose the problem, you have to identify the type of sound before looking for a solution.

Keep reading to learn about the different boiler noises and what they indicate.

When and How To Check Your Boiler

Your boiler is what keeps your home warm and toasty. To do that, it heats water and moves it through pipes throughout your home. In some cases, it heats the water to steam and moves that through the pipes and in others it uses a combination of heated water and air.

Your boiler doesn’t require much in terms of boiler maintenance. An annual checkup from our boilercare team at Oil 4 Wales is about all you need to do to keep your boiler working in fine order. But if you notice that your energy bills are increasing, your home isn’t heating up as fast, and there are noises coming from your boiler, you may have a problem that needs fixing immediately.

As soon as you notice that you have a noisy boiler, you should inspect it. Noises can occur even if everything seems to be working properly. It’s usually your first sign that something is wrong and it should never be ignored.

Before you grab your toolbox or call in the experts, you should make sure that the noise you’re hearing is actually coming from your boiler. Ensure that the noise you’re hearing is coming from the boiler and not from a radiator or central heating pipe.

When you’re sure that your problem is a noisy boiler, you can check the boiler itself for error codes. These might give you an indication of what’s wrong without having to dig any deeper. Check the digital display and any error codes against your owners manual, and if you don’t have your owners manual you can check online by searching your make and model.

Common Causes of a Noisy Boiler

Different causes of a noisy boiler will have different sounds. We’ve broken down the most common causes of a noisy boiler and what you might be hearing. With this information, you can diagnose your boiler problem before the experts even get there.

Scale Build-Up

The noises that you hear from scale build-up are also called ‘kettling’ noises (because it sounds similar to a kettle heating up). This is the result of limescale building-up on the heat exchanger in your boiler.

Most water that runs into our homes contains dissolved minerals. Those minerals tend to accumulate at the bottom of your tank and create deposits around the heat exchanger. This causes water to heat rapidly in some spots.

Those spots of rapidly boiling water send bubbles up through the tank. When that heated water reaches the cool water at the top of the tank, the action of the bubbles dissipates violently. Those are the kettling noises that you’re hearing, which can be similar to a knocking or banging.

The easiest fix for this problem is to use an additive that removes mineral deposits. You add that to the tank, drain it, and then refill it. If that doesn’t fix the problem, you might have to call in the professionals.

Water Temperature

Banking and knocking noises can also be caused by your water temperature setting. If your thermostat is set too high, the water in your boiler will boil too rapidly. This leads to the same issue as the mineral deposits – the boiling bubbles hit the cold water and dissipate violently, which causes a noisy boiler.

For a quick fix, you can try lowering your thermostat setting. But keep in mind that this will also lower the heat output of your system. If your boiler thermostat isn’t working correctly, you’ll ultimately have to have it fixed by the professionals like our Oil 4 Wales boiler care team. 

Air In the System

If you hear a whistling noise coming from your boiler, this can be caused by kettling, by air that’s trapped in your system, or by a loss of water pressure. Air can enter your system through broken valves, an expansion tank, or through breaches in connections or pipes.

Fixing this problem is a matter of releasing the trapped air from the system. But you’ll also need to diagnose how the air got into the system to stop it from happening again.

Water Supply

Kettling noises can also be caused by an insufficient amount of water in the boiler. Without enough water, the heat in the boiler can’t dissipate fast enough and the water in the tank boils, causing kettling.

Check your pressure gauge to be sure your boiler has the right water pressure. If it’s too low or too high, then increase it to the right pressure. You might also have to top up the water level.


Gurgling noises coming from the boiler can be caused by a frozen condensate pipe as well. To fix this issue, you’ll need to thaw the frozen pipe with hot water bottles and heat wraps. If the pipe isn’t accessible or at ground level, consider calling in a professional to thaw the pipe.

Call In The Oil 4 Wales Professionals

There’s no one single cause of a noisy boiler. Boiler noises can be caused by low water pressure, the air in your system, mineral deposits, and problems with your water temperature. Before you go any further, make sure you have a good idea of the cause of the noise and what needs to be fixed.

And although you might be okay to diagnose the problem, fixing it is a whole other issue. Unless you’re an experienced DIYer, boiler problems are best left to the professionals. Call us at Oil 4 Wales today to find out how our dedicated heating engineers can help.